B.L. Denny, and P.L. Guy (2009)
Australasian Plant Pathology, 38 (3), 270-276
Incidence and spread of viruses in white-clover pastures of the South Island, New Zealand
Sixty-two white-clover pastures were tested by enzyme linked immunosorbent assay (ELISA) for five viruses (White clover mosaic virus (WClMV), Alfalfa mosaic virus (AMV), Red clover necrotic mosaic virus(RCNMV), Soybean dwarf virus (SbDV), beet western yellows virus (BWYV)) and also for members of the potyvirus group. Only one pasture was found to be virus-free. WClMV and AMV occurred, often at high incidences, on farms in every region. RCNMV and SbDV occurred in more than half the pastures whereas BWYV and potyvirus infection was less common. There was a general reduction in virus diversity with increasing latitude, with the most northern farms having greater species richness (all 6 viruses present) than those in Southland (1-3 viruses present). There was a significant relationship between the presence of AMV, BWYV, RCNMV, SbDV and irrigation. Dairy farming also had a positive relationship with BWYV, RCNMV and SbDV. WClMV increase was monitored in six pastures and incidence was observed to increase geometrically in young pastures. The relatively high incidence of RCNMV is in contrast to the findings of previous studies on white-clover pastures and indicates that assessing this virus's effects on white clover is of high priority
B.M. Díaz, M. Nebreda, F. Salas, A. Moreno, M. García, and A. Fereres (2004)
Boletín de Sanidad Vegetal, Plagas, 30 (3), p. 623
Mallas impregnadas con insecticidas: un nuevo método para el control de plagas de cultivos hortícolas
[Insecticide-impregnated nets: a new method for controlling pests of horticultural crops]
(original language: Spanish)
In this work we evaluated the efficacy of the fencing PA 2001 01060 to protect a cabbage crop from insects and insect-transmitted virus diseases. A field experiment was conducted at Villa del Prado (Madrid, Spain) to test the efficacy of the nets. The experiment was conducted in a completely randomized plot design using 4 replicates and two different treatments (a control plot and a protected plot). Insect sampling was conducted to determine the direct incidence and population dynamics of key pests infesting cabbage in both treatments. Visual counting was used to determine the incidence of phytophagous insects feeding on the crop. Sampling of insects alighting on the crop was conducted by using horizontal green-mosaic tile traps (Irwin type) and yellow sticky traps. Insects monitored included aphids and other homopterans. Virus incidence in both treatments was assessed at the end of the crop growth cycle by ELISA test. The yield of cabbage under both treatments was compared. The results show that the number and the damage caused by Lepidoptera larvae and the number of aphids trapped by both types of traps were significantly lower in the protected plots than the control plots. However, no significant differences were observed in the number of Aleyrodes proletella L. and Cicadellidae trapped in yellow sticky traps. The number of adults and eggs batches of A. proletella were significantly higher in the control plots. The virus incidence was low, and therefore no statistical comparisions among treatments could be made. The viruses detected were LMV, CMV, BWYV, TSWV and AMV. No significant differences were detected in the yield of cabbage (mean weight/plant) between both treatments. Our results show that the insecticide-impregnated net described in this paper, with some modifications, can be an effective strategy to control cabbage pests.
R.A.C. Jones, and D.G. Ferris (2000)
Annals of Applied Biology, 137 (3), 259-271
Suppressing spread of alfalfa mosaic virus in grazed legume pasture swards using insecticides and admixture with grass, and effects of insecticides on numbers of aphids and three other pasture pests
Field experiments were sown with AMV-infected or healthy seed of burr medic (Medicago polymorpha) and grazed by sheep. Seed-infected plants acted as primary sources for virus spread by naturally occurring aphids. Admixture with annual ryegrass (Lolium rigidum), a non-host of AMV, and different insecticides were used in attempts to suppress virus spread. Sowing swards to provide the ratios 1:4 and 1:13 of medic:ryegrass plants diminished AMV spread in medic plants by 23% and 45% respectively. Applications of organophosphorus (demeton-s-methyl), carbamate (pirimicarb) and newer generation synthetic pyrethroid (alpha-cypermethrin) insecticides, all significantly decreased final AMV incidence. Alpha-cypermethrin was the most effective, suppressing AMV incidence by 87% (two sprays), 79% (one late spray) and 65% (one early spray). Two sprays of demeton-s-methyl decreased incidence by only 36%, while two and 2 weekly applications of pirimicarb diminished it by 29-65% and 35-70% respectively. AMV infection of medic seed harvested decreased by up to 76% in sprayed plots. Insecticide treatment did not prevent winged aphids from landing but numbers of wingless Acyrthosiphon kondoi colonising swards were suppressed by up to 92% by spraying with pirimicarb and up to 96% by alpha-cypermethrin. A. kondoi were much slower to recover with alpha-cypermethrin than with pirimicarb, the former still significantly diminishing its numbers 35 days after spraying. Alpha-cypermethrin was also very effective at suppressing Halotydeus destructor and Penthaleus major but not Sminthurus viridis. Greater effectiveness of insecticides in controlling spread of AMV in pasture than has been found previously with non-persistently aphid-transmitted viruses in annual crops seems due to the key role played by wingless aphids as virus vectors.
Emily E. Mueller, and Craig R. Grau (2007)
Plant Disease, 91 (3), 266-272
Seasonal progression, symptom development, and yield effects of Alfalfa mosaic virus epidemics on soybean in Wisconsin
The occurrence of Alfalfa mosaic virus (AMV) has increased in Wisconsin soybean fields in conjunction with the establishment of the soybean aphid (Aphis glycines). Field studies were conducted to determine the seasonal incidence of AMV-infected plants, progression of symptom severity caused by AMV, and the effect of AMV on soybean yield and seed quality. An isolate of AMV, collected from field-grown soybean, was introduced into plots by mechanical inoculation of plants at the V1 growth stage. The goal of the experiment was to achieve an incidence of AMV-infected plants of 0, 50, and 100% in 2002, and 0, 10, 25, 50, 75, and 100% in 2003. Severity of foliar symptoms was rated, and leaf samples were collected for serological assay (enzyme-linked immunosorbent assay [ELISA]) to estimate the incidence of AMV-infected plants from growth stages VC to R5. The maximum incidence of AMV-infected plants was 49% at growth stage R5, yet detection of the virus by ELISA dropped dramatically thereafter in both years. Incidence of AMV-infected plants accounted for 53 to 67% of the variability observed for severity of foliar symptoms in 2002 and 2003, respectively. Maximum yield loss ranged from 32% in 2002 to 48% in 2003 based on the difference in yield between noninoculated plots and plots with the highest incidence of AMV-infected plants. Incidence of AMV-infected plants explained 31% of the variation in yield in 2002 and 26% in 2003. An AMV incidence of 30% or greater was required for yield loss caused by AMV. Results of this study suggest that AMV has the potential to lower soybean yield and warrants further study.
L.J. Latham, R.A.C. Jones, and B.A. Coutts (2004)
Australian Journal of Experimental Agriculture, 44 (1), 57-63
Yield losses caused by virus infection in four combinations of non-persistently aphid-transmitted virus and cool-season crop legume
Field experiments provided quantitative information on the yield losses caused by virus infection within 4 different combinations of non-persistently aphid-transmitted virus and cool-season crop legume: Alfalfa mosaic virus (AMV) in chickpea, faba bean and lentil, and Cucumber mosaic virus (CMV) in lentil. Virus infection foci were introduced into plots and naturally occurring aphids spread infection from these to the other plants. Plants were tagged individually when typical virus symptoms first appeared during the growing period. Paired plant comparisons between symptomatic and asymptomatic plants were made to measure different yield loss parameters. Late infection with AMV in faba bean cv. Fiord diminished shoot dry weight by 41% and seed yield by 45%, but plants infected earlier recovered sufficiently from their initial shock reaction not to produce significant yield losses. In plants of lentil cv. Matilda first showing symptoms at different times, infection with AMV decreased shoot dry weight by 74-76%, seed yield by 81-87% and individual seed weight by 10-21%, while CMV diminished shoot dry weight by 72-81%, seed yield by 80-90% and individual seed yield by 17-25%. Early infection with AMV killed plants of chickpea cv. Tyson while later infection decreased shoot dry weight by 50%, seed yield by 98% and individual seed weight by 90%. The first tentative evidence for seed transmission of AMV in faba bean is reported with a transmission rate of 0.04%.
R.A.C. Jones (1992)
Australian Journal of Agricultural Research, 43 (5), 1229-1241
Further studies on losses in productivity caused by infection of annual pasture legumes with three viruses
Trials were done in 1988-90 to examine the effects of infection with three non persistently aphid-transmitted viruses on the productivity of manually inoculated spaced plants of annual pasture legumes growing in plots. Alfalfa mosaic virus (AMV) decreased herbage and root production (dry weights) of three subterranean clover (Trifolium subterraneum L.) cultivars by 20-49%. Cucumber mosaic virus (CMV) decreased herbage and root production of a murex medic (Medicago murex Wild.) cultivar by 78-90% and of two burr medic (M. polymorpha L.) cultivars by 56-82%. A mild isolate of bean yellow mosaic virus (BYMV) decreased herbage and root production of a subterranean clover cultivar by 31-40%, but with a severe isolate the corresponding losses were 60-63% in the same cultivar and 79-80% in another. The severe BYMV isolate caused losses in herbage and root production of 38-61% in two burr medic cultivars. Seed yield losses recorded due to infection of subterranean clover were 71% with AMV and 58-76% with BYMV (severe isolate); both viruses decreased seed size as well as seed yield. CMV decreased seed yield by 94% in a burr medic cultivar; it also decreased seed size.
R.Y. Wang, A. Kritzman, D.E. Hershman, and S.A. Ghabrial (2006)
Plant Disease, 90 (7), 920-926
Aphis glycines as a vector of persistently and nonpersistently transmitted viruses and potential risks for soybean and other crops
The recently introduced soybean aphid (Aphis glycines), which is widespread in the soybean-growing regions in the United States, is the only aphid able to develop large colonies on soybean. Although its potential as a vector of plant viruses is recognized, reports on virus transmission efficiency by this aphid species are limited. In the present study, we examined the ability of A. glycines to transmit several economically important viruses. The results showed that A. glycines transmitted the potyviruses Bean yellow mosaic virus (BYMV) and Soybean mosaic virus from soybean to soybean more efficiently than Myzus persicae. However, M. persicae transmitted the alfamovirus Alfalfa mosaic virus and the potyviruses Tobacco etch virus (TEV) and Tobacco vein mottling virus (TVMV) from tobacco to tobacco more efficiently than A. glycines. This is the first report to demonstrate that the soybean aphid can vector TEV and TVMV, two economically important tobacco viruses. This also is the first report to document successful transmission of BYMV by A. glycines. All attempts to transmit the nepovirus Tobacco ringspot virus by A. glycines were unsuccessful, regardless of the length of the acquisition and inoculation feeding periods. Although the luteovirus Soybean dwarf virus(SbDV) was widely distributed in red and white clover in Kentucky, it was not detected in soybean. All transmission experiments of SbDV by A. glycines were unsuccessful. A reverse-transcription polymerase chain reaction (RT-PCR) assay was developed to detect SbDV in single aphids using a pair of primers designed to amplify a 372-bp PCR fragment in the coding region of SbDV coat protein. Although A. glycines was not a vector of SbDV, the virus was detected in 100% of tested aphids by RT-PCR after a 24- to 48-h virus acquisition access feeding. The practical applications of RT-PCR in detecting persistently transmitted viruses are discussed.
J.H. Hill, R. Alleman, D.B. Hogg, and C.R. Grau (2001)
Plant Disease, 85 (5), p. 561
First report of transmission of Soybean mosaic virus and Alfalfa mosaic virus by Aphis glycines in the New World
The soybean aphid, Aphis glycines, has recently established in the United States and it was examined if this species can contribute to the transmission of Soybean mosaic virus (SMV ) and Alfalfa mosaic virus (AMV ). The aphid species Myzus persicae was tested for comparison. The data suggest that the introduced A. glycines can be an efficient vector of SMV, but a less efficient vector of AMV.
W. Pathipanawat, R.A.C. Jones, and K. Sivasithamparam (1997)
Australian Journal of Agricultural Research, 48 (7), 989 - 998
Factors influencing transmission of alfalfa mosaic virus through seed of annual medics (Medicago spp.) and the genetic control of seed transmission rate
Factors likely to influence rates of transmission of alfalfa mosaic virus (AMV) through seed to seedlings of annual medics (Medicago spp.) and genetic control of the magnitude of its seed transmission rate were investigated in plants from 17 early-flowering accessions of M. polymorpha and in progenies of crosses involving M. murex cv. Zodiac × accession 5320 as parents. Plants were graft-inoculated when 6 weeks old to ensure successful and uniform infection. To exclude variation in seed transmission rates due to virus isolate or temperature, only 1 AMV isolate was used and the plants were kept under uniform temperature conditions. In M. polymorpha, significant differences were found between accessions in the levels of AMV transmitted through seed to progeny seedlings, SA 8250 giving the highest mean level of seed transmission (52%) and SA 4188 the lowest (3%). Neither virus concentration nor symptom severity influenced the rates of seed transmission obtained. However, part of the variation in seed transmission rates found in these accessions was related to their flowering times, seed transmission rates increasing as the interval between inoculation and owering increased. In seed samples collected from individual graft-inoculated plants of M. murex from (i) the F2 generation from crosses and reciprocal crosses, and (ii) the backcross progenies, the rates of transmission of AMV through seed to seedlings ranged from 0 to 77% and showed a continuous pattern of variation. Also, there was evidence of transgressive segregation for the low seed transmission rate condition. This indicates that the low seed transmission rate condition for AMV in medics is quantitatively inherited and under polygenic control. In contrast, when the pods from F2 progeny plants from the crosses and reciprocal crosses were examined, the segregation ratios obtained revealed that the smooth pod character from parent accession 5320 was controlled by a single recessive gene, for which the name sp is proposed. The presence in a plant of gene sp, or of its spiny pod-determining allele from the other parent cv. Zodiac, was not correlated with low seed transmission rates of AMV. It is concluded that selection for low rates of seed transmission and a population breeding approach can be used to produce improved M. polymorpha and M. murex cultivars with good resistance to seed-borne AMV.
W. Pathipanowat, R.A.C. Jones, and K. Sivasithamparam (1995)
Australian Journal of Agricultural Research, 46 (1), 153-165
Studies on seed and pollen transmission of Alfalfa Mosaic, Cucumber Mosaic and Bean Yellow Mosaic Viruses in cultivars and accesions of annual Medicago species
Seed and pollen transmission of alfalfa mosaic (AMV), cucumber mosaic (CMV) and bean yellow mosaic (BYMV) viruses was investigated in annual medic species (Medicago spp.). For seed transmission studies with AMV, graft inoculation was used to establish early infection and maximize possible transmission rates to seedlings via seed, but with CMV and BYMV aphid and/or graft inoculation was used. For pollen transmission studies, pollen taken from virus-infected plants was used to pollinate healthy plants, the seed collected and seedlings tested. The rates of AMV isolate OUI-2 transmission to seedlings through seed produced on infected plants ranged from 6 to 53% for commercial cultivars and from 7 to 65% for accessions. Accession DZA 3181.1.1 of M. sphaerocarpos had the highest overall AMV transmission rate. Only two cultivars, cvv. Borung and Hannaford of M. truncatula, and accession SA 4268 of M. orbicularis, had transmission rates of less than 10%. The rates of CMV transmission to seedlings via seed produced on infected plants of the cultivars and accessions tested were 0.3 to 13%, the greatest being found in M. polymorpha cv. Serena, but 6 out of 11 had no detectable transmission. The rates of BYMV transmission to seedlings via seed of the cultivars and accessions tested were 0.3 to 1%, but in 12 out of 15 none was detected. AMV isolate OUI-2 was transmitted to 52% of seedlings via seed produced on healthy M. polymorpha cv. Circle Valley plants pollinated from infected plants. In contrast, no transmission to seedlings by either graft-inoculation or pollination of M. polymorpha plants was detected with a second AMV isolate, OUI-1, which appeared to have lost its ablilty to be seed transmitted. No CMV or BYMV transmission to seedlings via pollination of healthy plants with pollen from infected plants was detected in M. polymorpha cvv. Circle Valley or Santiago. When empty immature pods, and dissected seed coats and embryos from immature seeds produced on AMV-infected plants of M. polymorpha were tested, AMV isolates OUI-I and OUI-2 were detected in all pods and seed coats, but only in 59% of embryos with isolate OUI-2 and in none with isolate OUI-1. CMV was detected in 12% of embryos tested from immature seeds produced on CMV-infected M. polymorpha cv. Serena plants. Transmission of all three viruses through seed, and of AMV through pollen, is cause for concern in annual medic breeding and evaluation programs. Moreover, carry-over outside the growing season in medic pastures is possible through seed with all three viruses.